In recent years, semiconductor integrated circuits have become more complicated both in terms of packing density and the variety of device components that are included in a single circuit. As the productivity and performance demands increase, the size of integrated circuits, and the microelectronic dies (or “dice”), or semiconductor chips, on which they are formed continues to be reduced. As the devices become smaller and smaller, it is increasingly difficult to find room on each die for all of the desired components. Passive device components, particularly capacitors, can be greatly affected as the performance of such devices is often dependent on the surface area of die used.
Depending on the intended use of the semiconductor chip, one of the types of passive devices formed on the semiconductor substrate (e.g., wafer) may be a capacitor. “On-chip” capacitors are often used on integrated circuit devices such as converters, radio frequency (RF) circuits, and filters. In such applications, it is desirable for the capacitors to achieve a high capacitance density, as well as have a high “Q-factor,” low voltage and temperature coefficients, excellent matching properties, and long-term reliability.
One common type of on-chip capacitor used in the semiconductor industry is known as a “double poly capacitor” (DPC). A DPC typically includes two conductive plates stacked over a field oxide on the substrate with an insulating material, or dielectric, formed between. DPCs are relatively inexpensive to manufacture and can achieve reasonably high capacitance densities. However, DPCs have high voltage coefficients, and because of non-uniformity which often occurs in the thickness of the dielectric across the substrate, the capacitance density the individual capacitors formed on the same substrate varies, which leads to poor matching.
Another type of capacitor is known as a “metal-insulator-metal” (MIM) capacitor. MIM capacitors are known to have better electrical characteristics than DPCs, including smaller voltage and temperature coefficients. However, MIM capacitors add significantly to the manufacturing costs of the integrated circuit because several extra processing steps are required which are not typically used in the formation of the integrated circuits (i.e., are not part of standard complimentary metal oxide semiconductor (CMOS) processing).
Accordingly, it is desirable to provide a capacitor with improved electrical characteristics while maintaining low manufacturing costs. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.